In 5th-Generation mobile communication, the third state (i.e. an inactive state) of a user equipment (UE) is introduced on the basis of idle and active states. Under the inactive state, a base station may transmit downlink transaction data to the UE, and some downlink transaction data needs one or more feedback messages from the UE to inform the base station about a reception result of the transaction data.
In the related art, the base station transmits the transaction data to the UE if there is the transaction data to be transmitted to the UE. After receiving the transaction data, the UE determines whether one or more feedback messages for the transaction data is required, and initiates a random access request to the base station if yes, to trigger a random access process, during which the base station allocates an uplink resource to the UE through a signaling interaction with the UE. According to the allocated uplink resource, the UE transmits the one or more feedback messages, such as Acknowledgement (ACK) or Non-Acknowledgment (NACK) is fed back on the allocated uplink resource.